Thursday, April 4, 2013

Eosinophilic Granuloma Complex (EGC) in Cats - Part 1

Recently, I saw a pretty
dramatic case. A feline patient came in kind of looking like those people in that old Twilight Zone episode. You know the one:

Beauty is in the eye of the ulcer

It was an 12 year old
female cat named Lilly with a common
skin condition called the eosinophilic granuloma complex (EGC). The EGC isn’t
one disorder, per se. It is a collection
of skin disorders in cats that are often grouped together, because they have
the same basic underlying characteristic – infiltration of the skin by
eosinophils, a type of inflammatory blood cell that is commonly associated with
allergic or parasitic diseases.

The cause of EGC is not known,
however, an underlying allergy such as flea allergy, atopy (allergy to inhaled
environmental allergens) or food allergy has long been suspected. A genetic predisposition to EGC has also been
postulated. In some cases, EGC are triggered by an allergic response to
mosquito bites. Most of the time the
underlying allergen is never discovered. Any age cat may be affected, but it is
most common in young to middle aged cats. In some cats, more than one type of
eosinophilic skin disease can occur at the same time.

There are three manifestations of the
feline EGC, and poor Lilly had all three: the indolent ulcer; the eosinophilic
plaque; and the eosinophilic granuloma.

The
indolent ulcer (sometimes referred to as “rodent ulcer”, although I’m not sure
why) commonly appears as an erosion on the margin of an upper lip. Both lips can be affected, but in most cases,
it is unilateral. They appear reddish
brown and are well-demarcated and hairless. Sometimes, they are painful and
affect a cat’s willingness to eat. Most of the cases I’ve seen are mild
unilateral cases. Well, check out Lilly's upper lip. This is severe (I mean SEVERE) bilateral involvement.

The entire upper lip was gone,
basically. It was replaced by a severe ulcerated infiltrate of inflammatory
cells. Even the nose is a little bit
affected! The margins of the lips, on
the side are also affected, but you can’t see it in the photo.

The second
manifestation is the eosinophilic plaque. Eosinophilic plaques can appear
anywhere on the skin, but they are most commonly found on the abdomen and the
inside thighs. They may be singular, or
there may be multiple lesions. They appear raised, red, moist, and
well-circumscribed. They are very itchy,
and cats lick them constantly. Usually I
see these on the abdomen or on the inside of the thigh. This cat had two of them on his left front
foot, as you can see.

Again, very
dramatic. I’ve never seen them present as large, discreet masses like
this.

The third
way that the EGC can present is with eosinophilic granulomas. These are
sometimes called linear granulomas or collagenolytic granulomas. They often occur down the back of the thigh,
on the face, in the mouth, especially on the tongue or the roof of the mouth.
When they occur on the skin, they tend to be yellow or pinkish in color,
raised, hairless, with a characteristic linear configuration. When they occur
on the face or in the mouth, they tend to appear more nodular. One manifestation is to cause the lower lip
to swell, giving the appearance of a “fat lip”. Poor Lilly had them all over
her tongue and the roof of her mouth.
Her mouth was sensitive and I couldn’t get a good photo without
upsetting her.

Diagnosis
of eosinophilic skin disorders is usually made based upon the visual
appearance, however, sometimes a biopsy is necessary to rule out disorders with
similar appearances. No biopsy was
needed here. This was classic.

The optimal
treatment would be avoidance of the offending allergen. Strict flea control is essential, since flea
allergy may be a potential trigger for EGC. A feeding trial with a hypoallergenic
diet may be needed to identify an underlying food allergy. In most cases, the allergen cannot be
identified, and administration of immunosuppressive drugs is necessary to
control the clinical signs. The most
commonly prescribed drugs for this condition are corticosteroids. These drugs
can be given in pill form, or as a long-acting injection. Lilly was currently
receiving the corticosteroid dexamethasone.
According to the owner, it hadn’t really made much of a difference. Recently, the immunosuppressive drug
cyclosporine has been shown to be effective in controlling this condition. This is good news for cats that cannot or
should not be given corticosteroids (for example, diabetic cats and cats with heart
disease).

Lilly’s
lesions looked like they were a little infected, so I treated her with
antibiotics, in the form of a long-acting injection of Convenia, an antibiotic
that achieves effective blood levels which lasts 2 weeks. Convenia is great because it is usually
pretty effective for skin infections, and you don’t have to administer it
orally, which would have been difficult for this cat, given her tender
mouth.

So, you're sayin' all we need is some 'roids?!

As for
steroid treatment, I’m not a big fan of steroid injections, due to the
potential for adverse effects. I prefer
to give oral steroids, however, orally medicating Lily would be difficult,
and besides, the lack of response to her first trial with oral steroids was
discouraging. So, after discussing the
pros and cons of long-acting steroid injections, the owner consented to
treatment. I gave Lilly 20 mg of
methylprednisolone.

In two weeks I’ll recheck her to give the second Convenia
injection. I’ll take a photo and share
it with you. Two weeks after that, I’ll check her again, and will give a second
steroid shot if warranted. Sometimes it
can take two or even three injections.
Hopefully, she’ll need no more than two.

The prognosis for EGC varies, with
young cats often having a better prognosis than older cats. Stay tuned!

Dr. Arnold Plotnick (MS, DVM, ACVIM) blogs about professional and personal life experiences as an expert in the field of feline veterinary medicine.

Dr. Arnold Plotnick is a board-certified veterinary internist, feline expert, and the founder of Manhattan Cat Specialists. In addition to his medical work, he is an award-winning veterinary medicine writer.